CVE-2022-0850 Overview
CVE-2022-0850 is an information disclosure vulnerability in the Linux kernel's ext4 filesystem implementation. The flaw allows kernel memory contents to leak to userspace through the ext4_extent_header structure. The issue was identified through Syzkaller fuzzing and tracked by Red Hat under Bugzilla 2060606. A local, authenticated attacker can leverage the vulnerability to read sensitive kernel data and potentially impact system availability. The weakness is categorized under [CWE-200] (Exposure of Sensitive Information to an Unauthorized Actor). The upstream fix was committed to the Linux kernel mainline as commit ce3aba43599f.
Critical Impact
Local attackers with low privileges can exfiltrate sensitive kernel memory contents from the ext4 subsystem and trigger high-impact availability issues on affected Linux systems.
Affected Products
- Linux Kernel (multiple versions prior to the upstream fix in commit ce3aba43599f)
- Red Hat Enterprise Linux distributions shipping affected kernel versions
- Any Linux-based distribution using vulnerable kernel builds with ext4 enabled
Discovery Timeline
- 2022-08-29 - CVE-2022-0850 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2022-0850
Vulnerability Analysis
The vulnerability resides in the ext4 filesystem code path that handles extent header processing. When the kernel returns data structures related to ext4_extent_header to userspace, uninitialized or out-of-bounds memory contents are exposed. The result is unintended leakage of kernel memory into userland-accessible buffers. The flaw is locally exploitable and does not require user interaction. Although the primary impact is confidentiality loss, the issue can also be leveraged to disrupt availability, which is reflected in the high availability impact rating. The leaked data may include kernel pointers, cryptographic material, or other process-sensitive content useful for chaining with privilege escalation exploits.
Root Cause
The root cause is improper handling of the ext4_extent_header structure within the ext4 filesystem driver. Specific fields were exposed to userspace without proper sanitization or zero-initialization of memory regions. Refer to the Linux Kernel Commit Log for the precise code change addressing the issue.
Attack Vector
Exploitation requires local access with low-privileged user credentials. An attacker mounts or interacts with a crafted ext4 filesystem or invokes filesystem syscalls that traverse the vulnerable extent header processing path. The flaw is triggered without user interaction, and Syzkaller has demonstrated reproducible test cases. See the Syzkaller Bug Report for a verified reproducer.
No verified public exploit code is available. The vulnerability mechanism is documented through the upstream kernel patch and Syzkaller reproducer rather than weaponized proof-of-concept code.
Detection Methods for CVE-2022-0850
Indicators of Compromise
- Unexpected userspace processes performing repeated ioctl or filesystem syscalls against ext4 mount points
- Unprivileged users mounting or manipulating untrusted ext4 filesystem images
- Kernel audit logs showing anomalous ext4 extent operations from non-administrative users
Detection Strategies
- Inventory Linux hosts and verify kernel versions against the upstream fix commit ce3aba43599f
- Monitor for processes reading kernel filesystem structures through debugfs, dump_extents, or custom syscall sequences
- Correlate filesystem syscall telemetry with user privilege context to flag low-privilege users probing ext4 internals
Monitoring Recommendations
- Enable Linux audit rules (auditd) for ext4-related syscalls and mount operations on production systems
- Forward kernel and audit logs to a centralized data lake for retention and anomaly detection
- Track package and kernel update status across the fleet to identify hosts running unpatched kernels
How to Mitigate CVE-2022-0850
Immediate Actions Required
- Update the Linux kernel to a version containing upstream commit ce3aba43599f or your distribution's backported fix
- Apply vendor-supplied kernel updates from Red Hat and other distributions referenced in the Red Hat CVE Advisory
- Restrict the ability of unprivileged users to mount arbitrary ext4 filesystem images
- Audit local user accounts and remove unnecessary shell access on multi-tenant systems
Patch Information
The fix was committed to the mainline Linux kernel by Linus Torvalds. Distribution maintainers including Red Hat have issued backports. Reference the upstream commit at Linux Kernel Commit Log and track distribution-specific updates via the Red Hat Bug Report.
Workarounds
- Disable user_namespaces or restrict unprivileged mount capabilities where operationally feasible
- Enforce mandatory access controls (SELinux, AppArmor) to limit access to ext4 filesystem operations
- Apply kernel lockdown mode on systems where information disclosure to userspace must be tightly controlled
# Verify running kernel version and check for the fix
uname -r
rpm -q --changelog kernel | grep -i CVE-2022-0850
# Restrict unprivileged mounting on systemd-based systems
sysctl -w kernel.unprivileged_userns_clone=0
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
